There are all kinds of marketing strategies revolving around affiliate marketing, and these are far and away the most legitimate way to make money by posting ads. You’ll need to study up on the ad platforms you’re using, though — it’s not just something you can sit down and start doing in 10 minutes and then turn around and start making tons of money. (You can get ads set up pretty quickly — they just won’t convert very well if you don’t know what you’re doing.)
In your parent's day, the only way to make a living drawing comics was to get your comics into the newspaper or work for DC and Marvel. Today, you can draw comics about anything you want and start your own site to host them with a little money borrowed from mom and dad. Selling t-shirts and space for advertisers is a great way to earn a little money with your own comic.